PlasticPilot.net

Yes, this is your favorite aviation blog, even if this post title sounds much more like the typical anoucenement for a patch for a mysterious software. Apparently, the problems with the Eclipse 500 Very Light Jet FADECs is now solved.

The FADECs software did crash when it received an out of range value from the trhottles. According to AvWeb: “Eclipse says its solution will increase the range limit of the throttle quadrant assembly to prevent the fault condition from occurring.” Given the kind of problem - both FADECs failing at the same moment, when throttle is pushed full forward - this is not really a surprise to me.

Eclipse will deliver a software update that will remove the problem. It is not the first time in aviation history that a software patch will solve a problem, but given the mediatic buzz around the VLJs, and the Eclipse 500 in particular, this is gets more coverage than an Airbus patch.

The name of the patch I mentionned in this post is a personal inventon, trying to be fun, and to make you think. The serious problem that affected the Eclips will be solved by simply uploading a new firmware. I don’t know however if the Eclipse interface uses USB or Bluetooth.

Jokes put aside, I know many pilots that will feel uncomfortable with the concept of flying a software controlled plane. Most of them associate “software” with their own experience at home, with their PCs. Airplanes are not all the same, airlines are not all the same, and software are not all the same.

The development standards, and quality of software used aboard aircraft has nothing to to with what you have in your PC. The hardware is also different, and there are no third products that you can download yourself in the FADECs, making the environment much more controllable.

Another thing that make software sounds mysterious (and then dangerous) is that most pilots don’t understand exactly what it is, how it’s made, how it works, and what it does. A magneto, alternator or carburetor is much easier, and these things can be seen, touched, examined, dismantled, and inspected. You can’t do that with software.

Shall we get rid of software in our planes ? Hell NO ! There is no efficient engine management without electronics and software. There is no GPS, no RNAV tools without software. Without software, no cockpit integration is possible. Things like TCAS, GPWS, Mode-S transponders, FMS, and many others are all software based. Did I mention autopilots ?

As any airplane part, software can fail. It’s not because something is computer-based that there will be more or less failures. Just like a crankshaft, pump, belt, servo, landing gear assembly, fuel line, piston, windshield, voltage regulator, intercom, or any other mechanical or electrical component, software can fail.

This is exactly why there are so many different computers on board. For engines management, avionics, navigation, and so on, each system uses its own, separate hardware and software, to avoid crashing all of them at the same time. That would be bad. At least as bad as a failing wing-root, or a lost engine making the plane out of balance.

So please don’t be affraid of software simply because it can’t be seen or touched, and don’t compare aircraft embedded software with “quickly downloaded - quickly deleted” kind of stuff that fulfills most harddisks. Software is the next step in aviation, just like voice replaced morse code, and composite slowly replaces aluminium.

With the highly demanding validation and certification standards required in aviation, the risk levels remain minimal. Not zero, but well acceptable. Remember that safety is not defined as the absence of hazards, but the absence of unacceptable hazards.

According to a report from FlightGlobal, Diamond will announce at the next ILA show in Berlin the availability of its own engine, as an alternative to Thielert. The engine will also be made available to other manufacturers (a.k.a. Cessna for the C172 TDI).

This is not a new project, but it has certainly been accelerated by the recent financial problems by Thielert. I will keep an eye on that, and continue to keep you updated, also about other engines (Zoche, DeltaHawk, Mistral, …).

Read more about this topic in previous posts:

Hard times for Thielert

Cessna will not deliver C172 TDI in 2008

Older post about this project - A new plastic engine

The weather here over the last two weeks was simply perfect for flying. Blue skies with a few benign clouds in the afternoon, and temperatures reaching the high 20’s (celsius). Air is dry, and it’s not yet the CBs season. Simply cool. Before temperatures get in the 30’s it’s time for the seasonal warning about take-off performance.

You know, the good old “double penalty”. Warm air is less dense, so wings produce less lift, and engine produce less power. Nothing new under the sun, but a reminder never hurts. But what about turbo-diesel engines ? Shall not the turbo be insensitive to air density, at least to a certain level ? Let’s have a look.

The following graph shows the relation between temperature and take-off distance, all other parameters being equal : maximum take-off weight and no wind. If you’re used to the Piper performance graphs, this corresponds to the leftmost part. The Diamond graphs are of the same nature.

The aircraft I chose are the DA40-TDI, and the DA40-180 with fixed pitch propeller. I also added the PA28-181, because all three are used for the same kind of missions. The goal is not to compare the performances, but rather the slope of the curve, which indicates how much the temperature affects the performance.

When I made the first version of this graph, I used only the DA40-TDI and the PA28. I expected this difference in slope, because of the tubro, but it was so different that I also included the DA40-180. So, what does this graph teach us ?

1) Take-off performance degrades with temperature. Changing from 0° to 30° can increase the take-off distance by approximately 40%.

2) Turbo engines are less affected by increase in temperature.

3) As good as they are, turbo engines are not the perfect cure against performance degradation, simply because they don’t compensate for the aerodynamic penalty.

What is also interesting is that the DA40-180 has better performances for temperatures below zero degrees. I don’t have an easy explanation for that, and I also know that the C172 TDI performance is below the classical 172 in some areas of the operational domain, but this is not today’s topic.

When preparing your next flights, if the runway is a bit short, or if you fly with more passengers than usual, have a quick look at the performance charts. You’ll avoid any bad surprise, and have a good summer…